We're the user of the Xilinux over ZyBo. However, the ZyBo FPGA is so small and we'd like to switch to larger FPGA boards. After checking your website (http://xillybus.com/xillinux) , it seems the Zedboard with XC7Z020-CLG484-1 is the largest FPGA Xilinux-2.0 can support. Is it that case ? If not, what larger Xilinx FPGA board can user use to port over Xilinux2.0 as you know ?

As it says on that web page, Xillinux supports Zedboard, ZyBo and MicroZed, and hence Z020 is indeed the largest supported device.

Xillinux can be ported to any Zynq device. Note however that porting involves setting up the Zynq device, and then preparing the FSBL and creating a boot.bin by fusing it with the U-Boot. And possibly make changes in the Device Tree to match the new target. Quite some work, and it's not always easy to get it right.